How to keep cool in a blackout during a heatwave
鈥淚n times of very high聽electricity聽demand during a heatwave, power grids sometimes can鈥檛 manage, leaving many people without any electricity at all," said Professor Jay.
If there is no power for air-conditioning, and tap water is the only resource available,聽spreading聽it聽across聽the skin is the best way to prevent the body overheating irrespective of the climate,聽according to a new study from the University of Sydney.聽
Researchers from the University鈥檚 Thermal Ergonomics Laboratory聽simulated heatwave conditions to examine the effect of聽using water in different ways聽鈥撀爋n聽a person鈥檚聽core temperature, cardiovascular strain,聽risk of dehydration聽and comfort levels.聽
The results, in聽the prestigious聽Journal of the American Medical Association聽(JAMA),聽show that聽compared to just drinking water, applying normal tap water to the chest, arms, back, legs and face with聽a聽sponge in simulated heatwave聽conditions, lowered cardiovascular strain,聽halved the rate of dehydration聽and improve聽thermal comfort.聽聽
Immersing the feet in water above the ankles was also better than just drinking water, but not as effective as self-dousing: 鈥淪elf-dousing works better鈥痓ecause鈥痽ou can liberate a lot more heat with evaporation,鈥澛爏enior author聽Professor聽 别虫辫濒补颈苍别诲.听听
The , A preliminary study of the effect of dousing and foot immersion on cardiovascular and thermal responses to extreme heat, reported similar findings in both humid and very dry conditions.
Professor聽Jay,聽of the聽University鈥檚聽聽and the Faculty of said with numerous all-time temperature records being set across the world in 2019, developing evidence-based health advice to help protect people against heat-related illness in a range of different settings has never been more important.聽
鈥淭he electricity needed to sustain mass cooling with air conditioning during heatwaves is proving increasingly unsustainable, and the threat of power blackouts is becoming more common in densely populated cities across the world,鈥澛燩rofessor Jay said.聽
鈥淏lackouts are becoming more common in densely populated cities across the world.鈥�
鈥淚n times of very high聽electricity聽demand during a heatwave, power grids sometimes can鈥檛 manage, leaving many people without any electricity at all.聽
鈥淗owever,聽water pressure is usually preserved though so people still have tap water. We wanted to systematically assess how this water can be best used to聽lessen聽the physiological strain, such as increases in heart rate and progressive dehydration,聽that聽develops during extreme heat exposure.
鈥淯sually people are just told to drink water, but our findings show that the extra evaporative heat loss you聽can get from also applying water across the body with a sponge can make a difference. Immersing the feet in water can also help, but it鈥檚 not as effective as self-dousing.鈥�
Methods
Led by former聽University of Sydney PhD student Nathan Morris聽in聽a聽total of 90 trials, a mix of聽male聽and female聽volunteers were monitored聽for thermal strain (rectal temperature), cardiovascular strain (heart rate and blood pressure), risk for dehydration (whole body sweat rate), and thermal comfort (assessed using 120mm visual analogue scale).聽
Participants were exposed聽over a聽two-hour exposure to simulated peak conditions of two types of heat waves:聽one that was very hot and dry,聽replicating聽the peak conditions of the California heatwave in July 2018;聽and one that was cooler but more humid and with a higher heat index representing the peak conditions during the Chicago heatwave in July 1995, and Shanghai heatwave in July 2017.
奥丑补迟听苍别虫迟?听
Associate Professor Jay said聽the findings of the current study聽may also have聽potential application to cities in developing countries that have limited drinking water.聽
鈥淎ccording to the World Health Organisation,聽unclean drinking water is聽responsible for more deaths than聽even聽war;聽yet the number one public health recommendation in a heatwave is to drink water,鈥� Professor Jay said.聽聽
鈥淗owever, if water is sufficiently clean to apply to the skin, the subsequent evaporation might reduce the need for sweating to the extent that people may be able to stay hydrated without drinking as much water.鈥澛�
Professor Jay鈥檚聽team is currently聽examining the efficacy of a range of different low-resource cooling strategies that can be easily implemented in different heatwave聽settings聽by the elderly and聽by聽people with various medical conditions, for example,聽coronary artery disease and hypertension.聽聽
The聽team is聽also assessing the impact of different prescription medications on the type of advice that should be issued to the聽public in advance of extreme heat events.
